The present invention refers to a treadmill comprising at least one endless belt provided with a plurality of tread lamellae and guided around two deflection pulleys which are arranged one behind the other with parallel axes, said deflection pulleys being smooth in the area where they are in contact with the belt and said at least one belt being implemented as a flat belt, according to the generic clause of claim 1.
DE 25 03 118 B2 discloses a treadmill for physical training in the case of which an endless toothed belt is guided around two parallel deflection pulleys which are arranged one behind the other. This toothed belt is in engagement with complementary toothed rims on the deflection pulleys and can be driven by one or by both deflection pulleys. The toothed belt has attached thereto a plurality of tread lamellae-serving as a running surface between the deflection pulleys. In the area of the running surface, the tread lamellae are additionally supported by a supporting roller arrangement (cf. FIG. 3 of the cited Offenlegungsschrift DE 25 03 118 B2).
The transmission of force via toothed deflection pulleys and toothed belts generates an unpleasant, loud noise, which is found annoying when the treadmill is in operation. In addition a high degree of wear has to be reckoned with in the area of the teeth of the toothed belt.
In DE 42 38 252 C2, a treadmill is described, in which the transmission of force is essentially effected by means of a smooth portion of the respective deflection pulley to a smooth portion of the endless belt. The respective deflection pulley is additionally provided with a toothed-rim portion which is in engagement with a toothed-rim area (cf. FIG. 2 of the cited patent DE 42 38 252 C2). Since the transmission of force takes place essentially via the smooth portion of the deflection pulleys and the sliding-belt portion of the endless belt, less noise is generated when the treadmill is in operation.
However, due to the toothed-belt portion which is in engagement with the toothed-disk portion of the deflection pulleys, the noise generated when these components are in engagement is still rather loud and unpleasant. In addition, the production of the deflection pulleys, which consist of a sliding disk portion and a toothed-rim portion, and of the endless belt, which consists of toothed-belt portion and a sliding-belt portion, is complicated and expensive.
Offenlegungsschrift DE 25 03 118 B2, which has already been cited, additionally describes an arrangement in the case of which an endless belt is guided around two deflection pulleys, the belt being not implemented as a toothed belt. The noise generated by the toothed-belt/toothed-rim engagement is prevented in this way. The endless belt has secured thereto tread lamellae by means of suitable fastening pieces; these tread lamellae are, in turn, intended to form the running surface between the deflection pulleys. In the area of the running surface, the tread lamellae are supported by a suitable supporting roller arrangement.
However, in the case of such a deflection-pulley/belt arrangement, where said deflection pulleys and said belt have smooth surfaces, the danger exists that slip may occur between the driven deflection pulley and the belt. This makes the reproducibility of parameters inaccurate, said parameters being e.g. a speed measurement of the treadmill or a measurement of the distance which is to be simulated by the moving treadmill. In addition such slip may have the effect that the tread lamellae do not move parallel to one another.
Starting from this prior art, it is the object of the present invention to provide a treadmill which is adapted to be operated with the least possible noise, the movemement of the tread lamellae being stabilized in such a way that slip between the belt unit and the deflection pulley is prevented and the arrangement being economy-priced and reliable.
This object is achieved by a treadmill having the features of the characterizing clause of claim 1.
According to the present invention, each tread lamellae is provided with at least one engagement element projecting from the lower surface of said tread lamella, and at least two stabilizers are provided, which are connected to the deflection pulley such that they are secured against rotation relative thereto, a stabilizer of this kind being in engagement with an engagement element on the lower surface of a tread lamella when the circumferential area of the deflection pulley, which rotates in synchronism with the stabilizer, is in contact with the at least one belt, and at least one stabilizer being always in engagement with an engagement element.
In the treadmill according to the present invention, the force is transmitted without any toothed-belt/toothed-rim engagement. A possibly occuring slip is prevented by the existence of stabilizers. At least one of these stabilizers is always in engagement with an engagement element. Since the stabilizers are connected to the deflection pulley such that they are secured against rotation relative thereto, a 100% reproducibility of the speed of the treadmill in correspondence with the deflection pulleys is guaranteed in this way. Since toothed rims and toothed belts can be dispensed with, low-noise operation is guaranteed.
In accordance with a preferred embodiment, the deflection pulley comprises at least two deflection disks which are fixedly connected to a deflection shaft, and at least two corresponding belts are provided, which are guided on the at least two deflection disks, the at least one engagement element projecting from the lower surface of a tread lamella being arranged between the belts and the at least two stabilizers between the deflection disks.
This kind of arrangement reduces the amount of material that has to be used for the treadmill and permits a compact arrangement of the stabilizers.
In this embodiment, the tread lamellae in the area between the belts can have a T-shaped cross-section, the stem at the bottom of this T constituting the engagement element.
Such a cross-section of the tread lamellae prevents the lamellae from bending when a load is applied thereto. The engagement elements therefore fulfill a support function and represent respective engagement surfaces.
According to a first embodiment, the stabilizers extend radially and have such a length that they are adapted to be brought into engagement with the engagement elements of the tread lamellae.
It will be advantageous to provide at least four stabilizers, at least two respective ones of said stabilizers being arranged in spaced relationship with each other at the same angular position relative to the axis of the deflection pulleys.
Such an arrangement permits the individual stabilizers to be implemented as narrow elements, and this will save weight and material and reduce the noise produced when the stabilizers are brought into engagement with the engagement elements. Due to the fact that the stabilizers are arranged in pairs at identical angular positions, a parallel orientation of the tread lamellae is nevertheless guaranteed.
According to a second embodiment, the stabilizers extend from a deflection disk parallel to the deflection shaft on a radius of the deflection disk which permits an engagement of the stabilizers with the engagement elements on the tread lamellae.
This embodiment permits the amount of material used and the weight to be reduced still further.
According to a preferred arrangement of the second embodiment, a respective stabilizer on a deflection disk is arranged in opposed relationship with a second stabilizer on the other deflection disk.
An arrangement of this kind permits a compact structural design, without the stabilizers being visible from outside.
In accordance with another structural design of the second embodiment, the deflection disks can be interconnected by the stabilizers.
This means that the whole arrangement is stabilized still further.
In accordance with an advantageous embodiment, it is then possible to provide no central shaft in the area between the deflection disks; hence, material and weight will be saved again.
In the embodiments described, it will be advantageous when, in the area of engagement with the engagement elements on the lower surfaces of the tread lamellae, the stabilizers consist of an elastic material or are provided with an elastic coating. It will also be advantageous when the engagement elements on the lower surfaces of the tread lamellae are provided with a surface of elastic material. These measures serve to reduce the noise still further.
In the case of all embodiments, it will be advantageous when, in the circumferential direction of the deflection pulley, the size of the engagement areas of the stabilizers corresponds substantially to the distance between two engagement elements of two neighbouring tread lamellae, when these two tread lamellae are positioned on the deflection pulley.
A structural design of this kind guarantees a stabilization of the treadmill movement in both directions and permits an even more precise operation in this way.
It will also be advantageous when the stabilizers are arranged in pairs, the two stabilizers of one pair being arranged at opposite positions with regard to the axis of the deflection pulley.